This invention relates to olive oil based products, based on especially higher grades of olive oils like virgin olive oils, containing plant stanol esters and/or plant sterol esters and methods for preparing such olive oil based products, as well as certain plant stanol and/or sterol esters usable for the preparation of the olive oil based product.
Plant sterols are a group of compounds structurally very similar to cholesterol. The plant sterols occurring most frequently in nature are sitosterol, campesterol and stigmasterol. Vegetable oils and fats are the main source of plant sterols in our diet. In vegetable oils a major part of the sterols exists as fatty acid esters. Saturated plant sterols such as sitostanol and campestanol are present in our diet in small amounts. Daily intake of total stanols in the Finnish diet has been estimated to 30-80 mg/day. However, tall oil sterols contain 10-20% of plant stanols (mainly sitostanol and campestanol). Plant stanols can also be produced by hydrogenation to remove the double bond in corresponding plant sterols.
In recent years, much interest has been focused on the cholesterol-lowering properties of plant stanols and sterols with already many plant stanol or sterol enriched products such as margarines, salad dressings, bars and yogurts commercially available. Based on recent studies, a daily intake of 2-3 g plant stanols or sterols significantly reduces serum LDL cholesterol levels even when used as part of healthy recommended diets. Plant stanol and sterol enriched foods provide an enhanced dietary approach for lowering elevated serum total and LDL cholesterol levels. Enrichment of staple foods with plant stanols and/or sterols in their fatty acid ester forms is possible without compromising on taste or mouthfeel. Based on the cholesterol lowering efficacy and the fact that plant stanols are virtually unabsorbable, plant stanols are more preferable, but also blends of plant stanols and sterols or plant sterols alone can be used.
The best benefit from using plant stanols and/or sterols for lowering elevated serum total and LDL cholesterol levels is obtained when enriching staple foods. For example, in the northern part of Europe, margarine and spreads are very suitable food products for such enrichment, but for the southern part of Europe other staple food candidates need to be found. In this region, olive oil is a staple food of major importance. In addition, olive oil consumption is increasing also in other parts of the world due to the health reputation and the flavour of higher grades of olive oils. Olive oil contains naturally very low levels of plant sterols (typically  less than 0.2 g/100 g oil). In addition higher grade olive oils, such as virgin olive oils, contain quite high amounts of squalene, a precursor of cholesterol. The content of squalene varies, but extra virgin olive oil typically contains about 300 mg/100 g oil. Dietary squalene has been shown to increase serum cholesterol levels in man. Such an effect on serum total and LDL cholesterol levels may be counteracted by plant stanols and/or sterols. Therefore, there is clearly a need to make commercially available higher grade olive oils enriched with plant stanols and/or sterols, and to ensure that such olive oils have similar properties as normally used olive oils.
Virgin olive oils should remain clear when stored at 20xc2x0 C. for 24 hours. Typically, higher grades of olive oils, such as virgin olive oils, become cloudy with even clear crystallization occuring when stored for a prolonged time at refrigerator temperatures. An olive oil enriched with plant stanols and/or sterols should avoid cloudiness.
For the large-scale production of plant stanol and/or sterol esters, normally common vegetable oils or commercially available edible oils with modified fatty acid compositions are used. Enrichment of higher grades of olive oils, such as virgin olive oils, with plant stanol and/or sterol esters with fatty acids derived from such commercially available vegetable oils or their blends further enhances the precipitation of higher melting lipids at room temperatures and below. The formed crystals do not normally dissolve, even after prolonged storage at room temperatures. This problem cannot be solved, even by using the esterification of stanol and/or sterol fatty acids derived from currently commercially available vegetable oils with high levels of polyunsaturated fatty acids and low levels of saturated fatty acids, such as low saturated soybean oil (PUFA: 67 weight-%, SAFA: 7,9 weight-%), sunflower oil (PUFA: 64 weight-%, SAFA: 12 weight-%) or linola oil (PUFA: 70 weight-%, SAFA 11 weight-%).
U.S. Pat. No. 5,080,139 describes a method for refining virgin olive oil, in which the virgin olive oil is microfiltrated over a microfilter at temperatures from 15 to 35xc2x0 C. to obtain a virgin olive oil staying bright when subjected to a cold test at 0xc2x0 C. for 24 hours.
U.S. Pat. No. 3,751,569 describes clear cooking and salad oils having hypocholesterolemic properties. Into the liquid glyceride base oil is mixed 0.5-10 weight-% (calculated as free sterols) of a sterol fatty acid ester. The fatty acid moiety is defined as a C1-12 saturated monocarboxylic acid moiety or an unsaturated fatty acid with up to 24 carbon atoms. In one embodiment, the sterol fatty acid ester is prepared by perchloric acid catalyzed esterification of commercially-available free sterols with monocarboxylic acid anhydrides. The sterol fatty acid ester is added in an amount small enough to prevent precipitation at refrigerator temperatures. In the exemplified embodiment, the cooking or salad oil was prepared by dissolving a liquid glyceride base oil and a plant sterol monocarboxylic acid ester in a mutual solvent (such as hexane or diethyl ether) and evaporating the solvent. The solubility of different fatty acid esters of plant sterol in triolein are also presented, showing very low solubility for C12 (0.6%) and C16 (0.1%) saturated fatty acid plant sterol esters. The process and product disclosed in the ""569 patent suffers from at least two drawbacks. First, the use of fatty acids prepared from individual commercially-available free sterols is neither practical nor economical, as these starting products are quite expensive. Second, the perchloric acid catalyzed esterification process used in the ""569 patent is not a food grade process, as residual chloride remains in the product. Thus, the ""569 patent is not suitable for commercial applications.
GB Patent 1 405 346 teaches a process by which free sterols naturally contained in edible oils and fats are converted to fatty acid esters via an interesterification process. In addition, in Example 2 a method for producing vegetable oils with elevated sterol ester contents is described. However, the method taught is based on the interesterification of the entire oil blend, which based on physical properties cannot be executed for higher grades of commercial olive oils, such as virgin olive oils.
Saturation of a plant sterol blend to a corresponding plant stanol blend causes marked differences in the melting properties of the corresponding sterol/stanol esters with the same fatty acid composition. For example, vegetable oil based sterol ester with low erucic acid content, rapeseed oil fatty acids and corresponding stanol fatty acid ester showed the following amounts of solid fat contents (weight-% of total fat) at different temperatures as measured by NMR-technique:
The physical properties of stanol and/or sterol fatty acid esters can be tailor-made by changing the fatty acid composition of the fatty acid ester or by using different ratios of plant stanols and sterols in the ester.
In the present invention the problem with the precipitation/crystallisation of higher melting lipids in higher grade olive oils is overcome by dissolving plant stanol and/or sterol fatty acid esters with fatty acids derived from so-called high PUFA vegetable oils in higher grade olive oils, such as virgin olive oils, and crystallising any higher melting lipids from the olive oil at temperatures in the range from refrigerator temperatures to room temperatures to obtain a plant stanol and/or sterol fatty acid ester blend with a very low content of saturated fatty acid esters contained in the olive oil. The crystallisation temperature and time needed is dependent on the amount and type of stanol and/or sterol fatty acid ester used. By choosing the crystallisation temperature and time properly, the virgin olive oils either stay clear at refrigerator temperatures or become clear when the oil is removed from refrigeration and kept at room temperatures for a short period of time. Compared to U.S. Pat. No. 3,751,569, which shows a very limited solubility for e.g. plant sterol palmitate in a liquid glyceride base oil (0.1%), the presence of a plant stanol and/or sterol fatty acid ester blend with a high level of unsaturated fatty acids clearly enhances the solubility of stanol and/or sterol esters.
In addition, the present invention teaches plant stanol and/or sterol ester compositions usable for direct enrichment of virgin olive oils. Thus, an oil according to the invention can also be obtained by adding the appropriate amount of a plant stanol and/or sterol ester with a fatty acid composition containing more than 60%, preferably more than 65%, polyunsaturated fatty acids, and less than 5% saturated fatty acids. When olive oils which are clear at refrigerator temperatures are desired, a plant stanol and/or sterol ester with a fatty acid composition containing more than 60%, preferably more than 65%, polyunsaturated fatty acids, and less than 5% saturated fatty acids, preferably less than 3%, less than 2%, or most preferably less than 1.5% saturated fatty acids, such as stearic acid, is used. Such stanol and/or sterol fatty acid esters can be obtained by any esterification method known in the art, such as by esterification of a fatty acid blend or a fatty acid alcohol ester blend having the appropriate predetermined fatty acid composition. All percentage values above and throughout the specification are weight-%, unless otherwise indicated.
The term xe2x80x9cvirgin olive oilsxe2x80x9d is meant to include extra virgin olive oil, virgin olive oil, ordinary olive oil and lampante virgin olive oil, all defined according to the Official Journal of the European Communities No. L 39/2 (15.2.1992). In addition, any blend of virgin olive oils with lower grades of olive oils as defined by the Official Journal of the European Communities is covered by this definition. Preferably, such a blend contains at least 25%, more preferably at least 50%, and most preferably at least 75% virgin olive oils.
The term xe2x80x9colive oil based productxe2x80x9d is meant to include virgin olive oils, according to the above definition, enriched with a blend of plant stanol and/or sterol fatty acid esters. About 0.3-25 weight-%, preferably about 0.3-10 weight-%, more preferably about 1.5-10 weight-%, and most preferably about 3-10 weight-% of plant stanol and/or sterol fatty acid esters (calculated as free stanols) may be included in the olive oil based product.
The term xe2x80x9chigh PUFA vegetable oilsxe2x80x9d is meant to include vegetable oils or vegetable oil blends containing more than 50% polyunsaturated fatty acids and at least 7% saturated fatty acids in fatty acid composition. Typical high PUFA vegetable oils include sunflower oil, corn oil, soybean oil, low saturated soybean oil, safflower oil, cottonseed oil, linola oil or their blends. The amount of saturated fatty acids in the fatty acid composition is typically about 7.5-49%, more preferably about 8-25% and most preferably about 10-20%.
The term xe2x80x9cphytosterolxe2x80x9d is meant to include 4-desmethyl sterols, 4-monomethyl sterols, and 4,4-dimethyl sterols (triterpene alcohols) or their blends. The term xe2x80x9cphytostanolxe2x80x9d is meant to include 4-desmetyl stanols, 4-monomethyl stanols and 4,4-dimethyl stanols, and is preferably obtained by hydrogenation of the corresponding phytosterol. Typical 4-desmethyl sterols include sitosterol, campesterol, stigmasterol, brassicasterol, 22-dehydrobrassicasterol, xcex945-avenasterol. Typical 4,4-dimethyl sterols include cycloartenol, 24-metylenecycloartanol and cyclobranol. Typical phytostanols include sitostanol, campestanol and their 24-epimers, cycloartanol and saturated forms obtained by saturation of triterpene alcohols (cycloartenol, 24-metylenecycloartanol and cyclobranol). The terms phytosterol and phytostanol also include all possible natural blends of 4-desmethyl sterol and stanols, 4-monomethyl sterols and stanols, 4,4-dimethyl sterols and stanols and mixtures of natural blends. The terms phytosterol and phytostanol further include any individual 4-desmethyl sterol, 4-monomethyl sterol or 4,4-dimethyl sterol or their corresponding saturated (stanol) forms.
The terms xe2x80x9cplant sterolxe2x80x9d and xe2x80x9cplant stanolxe2x80x9d are intended to be synonyms to the terms xe2x80x9cphytosterolxe2x80x9d and xe2x80x9cphytostanolxe2x80x9d, respectively. xe2x80x9cSterolxe2x80x9d and xe2x80x9cstanolxe2x80x9d shall also mean xe2x80x9cphytosterolxe2x80x9d and xe2x80x9cphytostanolxe2x80x9d, respectively.
xe2x80x9cPolyunsaturated fatty acidsxe2x80x9d are herein defined as fatty acids containing two or more double bonds. Preferably, the double bonds have cis configuration, but one or more double bonds may be in trans configuration. It is known that many commercially available vegetable oils due to termal isomerisation in the deodorisation process contain a percentage level of polyunsaturated fatty acids containing one or more double bonds with trans configuration. In addition, the double bonds can be either so-called methylene interrupted or conjugated. Typical vegetable oil derived polyunsaturated fatty acids are linoleic, linolenic and xcex3-linolenic acid, but also polyunsaturated fatty acids from fish oils such as eicosapentaenoic and docosahexaenoic acid can be utilised.
By the term xe2x80x9csaturated fatty acidsxe2x80x9d is meant fatty acids with 4-24 carbon atoms not having any double bonds, thereby including both straight chain and branched fatty acids.
By the term xe2x80x9chigh PUFA stanol and/or sterol estersxe2x80x9d is meant stanol and/or sterol esters produced preferentially with fatty acids from high PUFA vegetable oils, but also fish oil derived polyunsaturated fatty acids or blends of vegetable and fish oil derived polyunsaturated fatty acids can be used.
The stanol and/or sterol fatty acid esters used in the present invention are preferably produced using a food grade process. A xe2x80x9cfood grade processxe2x80x9d is herein defined to include any process whereby the stanol and/or sterol fatty acid ester product is free from residual chemicals which are (1) undesired in the final product because they affect one or more of the qualities of the stanol and/or sterol fatty acid esters, or (2) harmful to a consumer from a food safety standpoint (e.g., the solvents or catalysts contain chlorides). There are a number of food grade processes known in the art, any of which may be suitable for producing the stanol and/or sterol fatty acid esters used in the present invention. Preferably, the food grade process is a solvent free food grade process. The stanol and/or sterol fatty acid esters may be produced by the method described in U.S. Pat. No. 5,502,045, for instance by transesterification of fatty acid alcohol esters obtained from high PUFA vegetable oils or their blends. Alternatively direct, preferably catalytic esterification methods such as those disclosed in U.S. Pat. No. 5,892,068, or enzymatic esterification methods such as those disclosed in EP 195 311 may be used.
Another possibility to produce stanol and/or sterol fatty acid esters is to utilise the excess of high PUFA alcohol esters present in the oily phase obtained after the esterification of high PUFA sterol and/or stanol ester according to the method described in U.S. Pat. No. 5,502,045. This mixture of high PUFA alcohol ester and sterol and/or stanol ester can as such be subjected to a fractionation step to remove higher melting sterol and/or stanol esters.
The stanol esters, sterol esters or their blends can preferably be produced by the method outlined in U.S. Pat. No. 5,502,045 using fatty acid alcohol esters with a predetermined fatty acid composition according to the present invention. The fatty acid alcohol esters can be produced by any process known in the art, such as solvent or detergent fractionation of alcohol fatty acid esters obtained from a high PUFA liquid vegetable oil or blends of high PUFA oils. Corresponding blends of fatty acid alcohol esters can also be obtained by distillation procedures under reduced pressure. Such distillation procedures can preferentially be used to remove saturated fatty acids with 16 or less carbon atoms. Fatty acid alcohol esters with the defined fatty acid compositions can also be obtained by alcoholysis of vegetable oils or oil blends with reduced contents of saturated fatty acids, obtained e.g. according to the U.S. Pat. No. 5,670,348.
The stanol and/or sterol esters with the desired fatty acid composition can also be produced by direct, preferably catalytic esterification methods, e.g. U.S. Pat. No. 5,892,068, between free fatty acids or fatty acid blends of the composition and the stanol and/or sterol. In addition, stanol and/or sterol esters can also be produced by enzymatic esterification e.g. as outlined in EP 195 311.
In addition blends of polyunsaturated fatty acids can be used for obtaining stanol and/or sterol esters with the desired composition.
Stanol esters and/or sterol esters with the desired fatty acid compositions can further be obtained by commercially applied fractionation processes, such as dry, detergent and wet-type fractionation of stanol and/or sterol fatty acid esters obtained by esterification of high PUFA fatty acids derived from e.g. vegetable oil or oil blends by methods based on e.g. the transesterification process outlined in U.S. Pat. No. 5,502,045, any direct preferably catalytic esterification process or by the use of an enzymatic esterification process e.g. as outlined in EP 195 311. Especially fractionation from solvents can be used for preparing desired sterol andlor stanol ester compositions. When using enzymatic esterification processes such as outlined in EP 195 311 the fractionation can preferably be carried out directly in the reaction solvent used in the esterification process after removing the enzyme and possible water phase.
The processes discussed above are just a few of the food grade processes which may be used to manufacture the stanol and/or sterol fatty acid esters in accordance with the invention.
In a preferred embodiment virgin olive oils, preferentially an extra virgin olive oil containing a predetermined blend of stanol and/or sterol fatty acid esters can be obtained by dissolving 5-50 weight-% (preferentially 5-25%) of stanol and/or sterol fatty acid esters obtained by an esterification process such as that disclosed in U.S. Pat. No. 5,502,045, for example by using a high PUFA vegetable oil or a mixture of high PUFA vegetable oils as a source for the fatty acids. This can preferentially be carried out as part of the regular refining process of virgin olive oils. The so-obtained stanol and/or sterol ester olive oil blend is heated and mixed to totally dissolve the stanol and/or sterol esters in the olive oil, after which a conventional xe2x80x9cwinterizingxe2x80x9d step or any fractionation process as known in the art is carried out. For example, a winterizing or batch dry fractionation type of process can be carried out at 0-30xc2x0 C., preferably at 5-25xc2x0 C. resulting in olive oil based products being clear at some point in the temperature range of 4-25xc2x0 C., more preferably at some point in the temperature range of 4-8xc2x0 C. All the olive oil based products made in accordance with the invention may become clear, in the cases of showing cloudiness at refrigerator temperatures, when removed from refrigeration and stored at room temperature, i.e. at some point in the temperature range of 18-30xc2x0 C., more preferably at some point in the temperature range of 18-25xc2x0 C. This means that the olive oil based product of the invention is clear at 30xc2x0 C. or more, preferably at 25xc2x0 C. or more, more preferably at 20xc2x0 C. or more, even more preferably at 18xc2x0 C. or more. If the product is stored at refrigerator temperatures (i.e., about 2-12xc2x0 C., preferably about 2-8xc2x0 C.), it is preferably clear at 8xc2x0 C., more preferably at 4xc2x0 C. As European consumers mostly are used to storing the oil at room temperatures, the olive oil based product may preferably be clear at 25xc2x0 C. or more, more preferably at 20xc2x0 C. or more, and most preferably at 18xc2x0 C. or more.
The crystallisation temperature and time can be altered depending on the amount and type of stanol ester and/or sterol ester used and the desired end product. After removing the solid part mainly made up of saturated fatty acids of the stanol and/or stanol ester by e.g. vacuum filtering, the obtained olive oil based product can be used as such or diluted with unprocessed virgin olive oils to obtain the desired content of plant stanol and/or sterol in the olive oil based product. Depending of the quality of the virgin olive oils, some part of the higher melting lipid components naturally contained in the olive oil will simultaneously be removed by the filtering process, and thus the process improves the clarity of the olive oil at refrigerator temperatures (i.e., about 2-12xc2x0 C., preferably about 2-8xc2x0 C.). It is obvious to those skilled in the art that any type of fractionation process in addition to the winterizing or batch dry fractionation type of processes can be utilised for crystallising and removing stanol and/or sterol fatty acid esters with higher melting points, e.g. sterol and/or stanol fatty acid esters based on saturated fatty acids. It is also clear to those skilled in the art that any filtration method known in the art can be used.
Another way of producing stanol and/or sterol esters with the desired fatty acid compositions is to utilise the excess of fatty acid methyl ester of the high PUFA sterol and/or stanol ester blend obtained after the transesterification disclosed in U.S. Pat. No. 5,502,045. After the drying step, the stanol and/or sterol ester fatty acid alcohol ester mixture is cooled to 5-25xc2x0 C., depending on the composition of the stanol and/or sterol ester produced, and the higher melting components are allowed to crystallize for 4-24 hours. Optionally additional fatty acid alcohol ester is added to facilitate the fractionation process. Any fatty acid alcohol ester may be used, but the use of high PUFA alcohol ester is preferred. After filtration, the clear oily phase is preferably deodorised to remove the excess fatty acid alcohol esters and to obtain a tasteless stanol and/or sterol ester. The stanol and/or sterol esters obtained as such can preferably be mixed into the virgin olive oils.
Plant stanol and/or sterol fatty acid esters with the desired fatty acid composition can furthermore be produced from fatty acids or fatty acid alcohol esters with appropriate composition. The so-obtained plant stanol and/or sterol fatty acid esters can be added directly to virgin olive oils to obtain olive oil based products taught by this invention.
In addition stanol and/or sterol ester compositions according to the invention can be produced utilising xe2x80x9cfatty acid starting materialsxe2x80x9d such as fatty acids, fatty acids alcohol esters or oils obtained by processes including e.g. utilising of micro-organisms, enzymes or new breedings of oil producing plants. The sterol and/or stanol part may be obtained from any sterol and/or stanol source, e.g. from the paper pulping industry or from the processing of vegetable oils. New breedings producing elevated amounts or more attractive compositions of suitable sterols and/or stanols produced by conventional methods or genetic modifications are also included as possible raw-materials for the production of stanols and/or sterols. Preferably, the stanol and/or sterols are thereafter utilized in a food grade process to produce the olive oil based product of the invention.
In a preferred embodiment of this invention, virgin olive oils are enriched with plant stanol fatty acid esters with a predetermined fatty acid composition. Also blends of plant stanol and sterol fatty acid esters or plant sterol fatty acid esters can be used.
The following examples are presented in order to disclose the present invention in more detail. All the percentages given are in weight-%.